THE HYDROLOGY OF THE 

 SOUTHERN OCEAN 



By G. E. R. Deacon, B.Sc. 

 (Text-figs. 1-22; Plates I-XLIV) 



INTRODUCTION 



The series of observations which the Discovery Committee has been conducting 

 for some years past on the hydrology and plankton of the South Atlantic and 

 neighbouring parts of the Indian and Pacific Oceans was extended by a circumpolar 

 cruise in 1932-3 to include the whole of the Southern Ocean. The work in the Indian 

 and Pacific Sectors was carried out entirely during the winter months, and the data are 

 therefore not sufficient for a complete examination of the hydrology, but so much has 

 been discovered that is of immediate importance to those who are continuing the work 

 and to those who are studying the plankton, that the following account has been 

 prepared. 



The report is based largely upon the observations made during the second com- 

 mission of the R.R.S. 'Discovery II', when the Antarctic Continent was circum- 

 navigated, but all the data collected during the first commission and by the Committee's 

 other vessels have been taken into consideration. In one or two instances a preliminary 

 use has also been made of the material collected during the third voyage which was 

 successfully concluded in 1935. 



The author has already given a general account of the hydrology of the South 

 Atlantic Ocean, but since some of the problems of this ocean have been brought much 

 nearer solution by the examination of other aspects of the same problems in the Indian 

 and Pacific Oceans, this report has a good deal to add to the previous one. It has also 

 been found necessary to extend the accounts of some of the Atlantic currents in view of 

 their importance to the world-wide movements. 



Throughout the whole of the Southern Ocean the meridional circulation of water is 

 very similar to the Atlantic circulation illustrated in Fig. 1 . On all sides of the pole the 

 Antarctic water spreads northwards in a shallow layer at the surface until it reaches 

 the Antarctic convergence where it plunges abruptly to a deeper level to continue its 

 northward movement as the Antarctic intermediate current. 



The observations made during the circumpolar cruise have shown that the latitude 

 of the convergence is determined by the movements of the deep and bottom waters. 

 In each sector of the Southern Ocean there is a warm deep current moving towards the 

 south ; the current is almost horizontal until it approaches the Antarctic region, but then 

 climbs steeply towards the surface over a current of Antarctic bottom water which 

 sinks in the opposite direction, and continues towards the south at a much lesser depth 



